This invention relates to a water containing explosive cartridge, of which at least one end face is constituted of a star clip portion including an inner lid, and a process for producing the same.
The water containing explosive cartridge is also good in sealability of water containing explosives, having substantially flat end faces rather than being convex at both end faces, particularly at the end face on the sealed side after filling of water containing explosive, and is also suitable for insertion of a detonator.
In recent years, water containing explosives such as water gel explosives, slurry explosives, emulsion explosives are becoming widely used in a large number of fields for industrial explosives, and increased progressively in amounts used in the same fields.
Whereas, as to the wrapped form of such water containing explosives, namely the cartridge is essentially required to have a structure such that the contents will not flow out from the cartridge, because the water containing explosive to be wrapped contains a considerable level of water, and also most of the water containing explosives are in the so called gruel-like state having fluidity. For this reason, sealability is of great concern and, consequently, most of the wrapped products are prepared with the use of a synthetic resin film in the form of the so-called sausage type clipped at both ends.
As a wrapped form different from the sausage type, U.S. Pat. No. 4,033,264 discloses a wrapped product of a water containing explosive with the use of a paper. However, the technique disclosed in U.S. Pat. No. 4,033,264 performs paper wrapping by means of a Rollex wrapping machine (e.g. U.S. Pat. No. 3,248,847) which has been used for wrapping a nitroglycerine-based explosive (dynamite) and, it has been required to select a specific polymer for gel formation and a metal ion for imparting friable or non-cohesive property to the water-bearing gelled explosive which the material to be wrapped. Therefore, the detonation velocity obtained, which is the most important performance of explosive, was only about 2700 m/sec to pose a problem in practical application. Under such a situation, in spite of the proposal of a paper wrapped type as disclosed in U.S. Pat. No. 4,033,264, water containing explosives have been still predominantly in the wrapped form of the sausage type as described above.
The cartridge of this sausage type, while being excellent in water resistance and handling of bench blasting pitfall, has the drawbacks as mentioned below, as compared with the prior type dynamite cartridge:
(1) Since both end faces are crimped with clips, they become convex faces which are poor in continuity of explosion;
(2) Due to convex end faces, detonators can be poorly inserted thereinto and parent dies (cartridges mounted with detonators) can be prepared with difficulty;
(3) Due to convex end faces, overlapping of cartridges will occur within bores during charging of cartridges, whereby charging work can be done with difficulty;
(4) Immense hygroscopic contamination is caused by residual powder at the clip crimping portions during storage.
Various drawbacks as mentioned above are caused primarily by the convex shape of the end faces of the sausage type cartridges, and most of the problems will be overcome if the both end faces can be made end faces consisting of flat planes (hereinafter merely called flat end faces) perpendicular to the longitudinal axis. However, unless the material of the cartridge is made a rigid material, the cartridge will be readily deformable, so long as the contents have fluidity, so that it has been very difficult to seal the cartridge end face, particularly the end face on the side to be sealed as the flat end face in contact with the upper face of the water containing explosive after filling of the water containing explosive.